Ships, sea bed structures and harbor facilities are getting damaged as soon as they are exposed on the ocean because many forms of marine organisms stick to them to cause damage. For an example, when marine organisms adhere to the surface of a ship and are growing thereon, frictional force between the surface and seawater increases during navigation, causing increase of fuel expenses.
To prevent the pollution by oceanic lives, the conventional antifouling paint composition prepared by mixing vinyl chloride resin or vinyl resin with rosin, a plasticizer and an antifouling agent, has been used. However, copper, mercury and organotin compounds used as an antifouling agent for the conventional antifouling paint composition cause maritime environmental pollution, which has been a serious environmental problem to be solved.
U.S. Pat. No. 4,191,570 and English Patent No. 1,457,590 describe the self-polishing antifouling paint composition in which organotin compound such as tributyltin oxide is combined as an ester form with unsaturated monomer such as acrylic acid or methacrylic acid so that the compositions can be hydrolyzed by seawater. The antifouling paint composition described in the above patents releases organotin from the seawater contact area and carboxyl group of this area forms a salt. As a result, the resin becomes hydrated and swelled, so that the resin is fallen apart from the surface to form another surface layer. This composition has been the most common antifouling paint so far but the use of this composition has been prohibited by International Maritime Organization since 2003 because the organotin compound released from the paint causes toxicity in marine organisms and imposex by being accumulated in oceanic lives.
An alternative paint has been developed to overcome the above problems, which is a tin-free antifouling paint. This paint is prepared by mixing tin-free resin with cuprous oxide and an organic antifouling agent. However, this antifouling paint also has a problem of toxicity caused by cuprous oxide and the organic antifouling agent eluted from the surface of a film of paint.